1. Field of Invention
The present invention relates to an object detecting device for sensing an object, such as a workpiece placed on a workpiece holder of a machine tool.
2. Discussion of Related Art
Object detecting devices, also sometimes referred to as edge finders are known, which detect an object, and in particular an electrically conductive workpiece, upon contacting the object. Conventional edge finders have a cylindrical housing of metal which is inserted into the tool holder of a machine tool. The tip of the edge finder is formed by a spherical probe. Inside the edge finder, a power supply is provided. Also, a light source is provided which emits light upon detection of a workpiece placed on a workpiece holder of the machine tool.
More specifically, the power supply, the light source, the probe, the tool holder, the workpiece holder and the workpiece form part of an open electrical circuit. When the probe contacts the workpiece, the electrical circuit is closed and the light source activated.
Such edge finders are known from DE-A-2813853 and DE-U1-29518671.
In order to process the detection of a workpiece, for example to determine the position of the workpiece on the workpiece holder or the dimensions of the workpiece, an operator has to operate an external processing unit upon cognition of light emitted by the light source. In response thereto, the processing unit may store current parameters of the machine tool, such as the current position of the tool holder. Such processing is inexact since it depends on the manual operation by the operator. It is also inconvenient because it constantly involves the operator.
Accordingly, it is an object of the present invention is to provide a simple sensing device which does not require manual operation in order to process object detections.
Another object of the present invention is to provide an object detecting device which supplements existing sensing devices in order to provide for automatic detection processing.
Other objects of the present invention will become apparent from the following description of the present invention and embodiments thereof.
One aspect of the present invention regards a detector assembly for sensing an object, the detector assembly includes an object sensing component that has a probe for contacting an object and a light source that emits light upon the probe contacting the object. A light detector is attached to the object sensing component, wherein the light detector detects the emitted light and generates an electrical signal.
The object detecting device according to the present invention thus provides for an automatic detection of light emitted by the light source when a workpiece is detected. Responsive to the light detection, the detector generates an output signal which is transmitted to an external processing unit for further signal processing (e.g. a computer). For example, the processing unit includes a counter of a position measurement system of a machine tool which measures the position of a workpiece holder relative to a tool holder by increments. An output signal of the detector halts the counting or sets the counter to a stored numeric value. Alternatively, the processing unit may process additional signals provided by the machine tool in order to determine the position of the workpiece on the workpiece holder, or the workpiece dimensions.
Such automatic detection does away with the disadvantages resulting from a manual operation of the external processing device upon user cognition of an activation of the light source.
In one embodiment of the present invention, the light detector is contained in the light detector housing that is attachable to an object sensing component housing. The light detector housing is attachable to the object sensing component housing by magnetic force. This provides for an easy assembly and disassembly of an object sensing component, which includes an object sensing probe and the object sensing component housing, and a detector assembly, which includes the light detector and the light detector housing. Also, the relative position of the detector assembly to the object sensing component is easily adjustable to ensure that light emitted by the light source is reliably detected by the light detector.
In another embodiment of the present invention, a clamp is mounted to the light detector housing for clasping the object sensing component housing. Thereby, a simple mechanical connection of the detector assembly and the object sensing component is provided which is easy to manufacture.
In another embodiment of the present invention, a lens in the light detector housing is arranged before the light detector to focus the light from the light source on the light detector.
In another embodiment, the light detector housing includes having the aperture located in between the light detector and the light source when the light detector housing is attached to the object sensing component housing.
The aperture ensures that no light can impinge on the light detector when the detector assembly is disassembled from the object sensing component, thus preventing false detections which may result from ambient light entering the light detector housing.
Preferably, the aperture is formed by at least one shutter operable by a force acting on at least one actuator associated with the shutter, wherein the actuator projects from the light detector housing such that a force is applied thereon by the object sensing component housing when the light detector housing is attached thereto.
Thus, automatic mechanical operation (i.e. opening and closing) of the aperture is effected by assembly/disassembly of the detector assembly and the object sensing component. Such an aperture is simple and inexpensive.
A second aspect of the present invention regards an object detecting device for sensing an object, the object detecting device including an object sensing component housing and a light source arranged at or in the object sensing component housing. A probe is arranged at the object sensing component housing and contacting an object thereby to detect the presence of the object and causing the light source to emit light. A light detector detects the light and includes a light detector housing attached to the sensing device housing, the light detector connected to a processing unit for processing the light detected by the light detector.
Such an object detecting device may also be referred to as an edge finder.
The object detecting device of this aspect of the present invention may be obtained by converting existing conventional edge finders. Accordingly, the advantages of an automatic light detection are provided simply without requiring full replacement of existing equipment.
The light detector housing may be attachable to the object sensing component housing by magnetic force. In particular, the object sensing component housing may be of metal or may include a metal portion in the proximity of the light source, and the light detector housing may include one or more magnets to interact with the metal object sensing component housing or the metal portion of the object sensing component housing. Thereby, a simple connection of the light detector housing and the object sensing component housing is provided which is convenient to handle.
Preferably, those sides of the object sensing component housing and the light detector housing which are to contact one another for attachment of the light detector housing to the object sensing component housing are shaped complementarily to each another. Thereby, a reliable connection between the light detector housing and the object sensing component housing is provided. Also, ambient light is prevented from entering the light detector housing at the (preferably transparent) outer wall of the light detector housing which abuts the object sensing component housing.
In particular, the object sensing component housing may be cylindrical, and that side of the light detector housing which abuts the object sensing component housing is curved inversely to the corresponding portion of the cylindrical object sensing component housing. This embodiment reflects that most existing object detecting devices are cylindrical. Thus, conversion of existing object detecting devices is facilitated.
In one embodiment, the object sensing component housing includes a window, and the light source is arranged within the object sensing component housing to emit light through the window. The window may extend all around the circumference of the object sensing component housing. Thus, the positional adjustment of the object detecting device is facilitated. Alternatively, one or more separate windows may be arranged around the circumference of the object sensing component housing.
The light detector may be a photo transistor, a photodiode or a photoresistor which is sensitive for the visible light of the light source.
Another aspect of the present invention regards an object detecting device for sensing an object, the device including a housing, a light source arranged at or in the housing, for indicating that an object has been sensed. A probe is arranged at the housing and contacting the object thereby to detect the presence of the object and causing the light source to emit light. A light detector is attached to the housing at a position to detect the light emitted from the light source.
Another aspect of the present invention regards an object detecting device that includes a housing and a light source at or in the housing, for indicating that an object has been sensed. A probe is linked to the light source, for sensing the object and for activating the light source when the object is sensed and a light detector assembly attached to the housing for coupling the light source with a processing unit.